1. Field of the Invention
The present invention provides a determination of surface areas by measurement of polyvinylpyrrolidone adsorption in solution.
2. Brief Description of the Related Art
Smectitic minerals may have a dramatic, sometimes dominate, effect on the physical and chemical properties of soils and sediments because of their high surface areas, high cation exchange capacities and swelling properties. However, the quantification of smectite minerals in sediments has remained problematic (see e.g., Srödon, Jan, Drits, Victor A, McCarty, Douglas K, Hsieh, Jean C C, and Eberl, Dennis D (2001) Quantitative x-ray diffraction analysis of clay-bearing rocks from random preparations. Clays and Clay Min. 49:514-528). The fundamental question of “what is a smectite?” has been a popular philosophical topic among clay mineralogists. A traditional mineralogic definition, based on the mineral chemistry and structure, is difficult to apply both because of the wide range of possible compositions, and because of the practical difficulty of isolating any single pure clay phase from a mixture for accurate chemical analysis. In fact, compositional variability between and within individual smectite particles may mean that smectitic minerals actually defy the strict definition of a phase (see e.g., May, H M, Kinniburgh, D G; Helmke, P A, and Jackson, M L (1986) Aqueous dissolution, solubilities and thermodynamic stabilities of common aluminosilicate clay minerals; kaolinite and smectites. Geochim. Cosmochim. Acta, 50:1667-1677). Before the work of Nadeau (Nadeau, P. H. (1985) The physical dimensions of fundamental clay particles. Clay Minerals, 20:499-514; and Nadeau, P. H.; Wilson, M. J.; McHardy, W. J.; Tait, J. M. (1984) Interstratified clays as fundamental particles. Science. 225:923-925. 1984, 1985) and others, a practical working definition of smectites was any clay that swells to 17 Å when exposed to ethylene glycol vapor. However, this functional definition has become increasingly problematic as additional work has shown that illite-smectite mixed layer clays can be dispersed into fundamental particles. When in a dispersed state, the illite particles display only a 10 Å XRD peak (see e.g., Eberl, D. D.; Nüesch, R; Sucha, V; Tsipursky, S (1998) Measurement of fundamental illite particle thicknesses by X-ray diffraction using PVP-10 intercalation. Clays and Clay Minerals, 46: 89-97). However, when dried, the interfaces between the reassembled illite particles can be X-ray coherent, and yield layers that expand to 17 Å in ethylene glycol. Thus, a sample of “pure illite” particles can produce the characteristic smectite swelling with glycolation, even though strictly speaking, no smectite is present. A more accurate working definition of a smectite is a 2:1 clay which, when Na saturated, can be dispersed as a single unit cell thick particle in aqueous solution, which is the presently used concept of a smectite.
Traditional measurements of surface areas on dried samples may not accurately reflect the surface areas of material in suspension. For example, smectite particles can be dispersed in solution as single unit cell (˜1 nm) thick particles, and this is the surface area which controls the physical and chemical properties of smectites. However, when smectites are dried, they form XRD coherent aggregates, making the interfaces between the particles inaccessible to most traditional measures of surface area, such as N2 adsorption (BET), which must be performed on solid samples.
X-ray diffraction (XRD) has been found to be an inappropriate method for quantifying these smectite particles. Completely dispersed smectite particles have no (001) XRD peak, because a single unit cell does not have a repeat distance in the c direction (see e.g., Eberl et al., 1998, identified above). The a-b plane of smectites generate XRD peaks (particularly the (060)), but these peaks closely overlap with illites and micas, which are nearly ubiquitous in natural samples. When smectites and illites are dried, the particles are easily deformed by strong surface interactions to form highly oriented and coherent aggregates of illite/smectite crystals (see e.g., Blum, Alex E. (1994) Determination of Illite/Smectite Particle Morphology using Scanning Force Microscopy. (in: Scanning Probe Microscopy of Clay Minerals, K. Nagy and A. Blum eds.) Clay Min. Soc., 171-202) which generate the commonly observed (001) diffraction peaks by interparticle diffraction (see e.g., Nadeau, et al., 1984, identified above). However, in complex mixtures containing minerals in addition to smectite, both the “stacking” efficiency and the crystal orientation relative to the X-ray beam become highly variable, making quantification of smectites using the (001) XRD peaks inaccurate.
During sorption of inert gases in a dry environment, (e.g., using N2, Kr or various organic vapors by the Brunnuer, Emmet and Teller (BET) method) the gas does not access the “internal” surfaces between coherently stacked crystals, and therefore, grossly underestimates the smectite surface area that is exposed to solution (see e.g., Aylmore L. A. G. and Quirk, J. P. (1967) The micropore size distributions of clay mineral systems. J. Soil Sci., 18:1-17). Smectites also may be quantified by measurement of the cation exchange capacity (CEC). However, the CEC of smectites can vary by almost a factor of two, leading to a similar error in using cation exchange capacity to quantify smectite abundance. In addition, other minerals and organic matter may also contribute to the CEC in an unquantifiable manner.
Although the sorption of ethylene glycol monoethyl ether (EGME) has been suggested as a technique to quantify smectite abundance, recent works (see e.g., Chiou, Cary T; Rutherford, David W (1997) Effects of exchanged cation and layer charge on the sorption of water and EGME vapors on montmorillonite clays. Clays and Clay Minerals, 45:867-880; and Rutherford, David W; Chiou, Cary T; Eberl, Dennis D (1997) Effects of exchanged cation on the microporosity of montmorillonite. Clays and Clay Minerals, 45:534-543) has shown that sorption of EGME is highly dependent on the EGME partial pressure, exchangeable cation and layer charge as well as void sizes and organic carbon content.
Polyvinylpyrrolidone (PVP, CA#9003-39-8) is a widely used industrial surfactant, emulsifier and adhesive, with applications including hair spray, textile dye stripping, extender for blood plasma, ink-jet printing, tablet binder in pharmaceuticals, and the adhesive at both ends of toilet paper rolls. PVP polymers are synthesized from monomer units. PVP is available in a variety of chain lengths with molecular weights (MW) ranging from 10K to 1200K, which corresponds to chains of about 90 to 11,000 monomers.
PVP has been widely investigated as a surfactant (see e.g., Frances, C. W. (1973) Sorption of polyvinylpyrrolidone on reference clay minerals. Soil Sci., 115:40-54). Levy and Frances (Levy, R. and Francis, C. W. (1975a) Interlayer sorption of polyvinylpyrrolidone on montmorillonite. J. Colloid Interface Sci., 50:442-450) first studied the sorption behavior of PVP on montmorillonites, and Levy and Frances (Levy, R. and Francis, C. W. (1975b) A quantitative method for the determination of montmorillonite in soils. Clays and Clay Min., 23:85-89) proposed using a XRD technique utilizing intercalated PVP to quantify the amount of montmorillonite in a sample in the presence of other swelling clays, such as vermiculite. The nature of PVP binding to montmorillonite surfaces has also been studied (see e.g., Gultek, A., Seckin, T., Onal, Y., and Ickuygu, M. G. (2001) Preparation and phenol captivating properties of polyvinylpyrrolidone-montmorillonite hybrid materials. J. Appl. Polymer Sci., 81:512-519; Séquaris, J. B M., Decimavilla, S. Camara and Ortega, J. A. Corrales (2002) Polyvinylpyrrolidone sorption and structural studies on homoioic Li-, Na- K- and Cs-montmorillonite colloidal suspensions. J. Colloid and Interface Sci., 252:93-101; and Séquaris, J. B M., Hind A., Narres, H. D. and Schwuger, M. J. (2000) Polyvinylpyrrolidone sorption on Na-montmorillonite. Effect of the polymer interfacial conformation on the behavior and binding of chemicals. J. Colloid and Interface Sci., 230:73-83). There have been studies of PVP sorption on silica (see e.g., Cohen Stuart, M. A., Fleer, G. J., and Scheutjens, J. M. H. M. (1984) Displacement of polymers. II. Experiment. Determination of segmental sorption energy of poly(vinylpyrrolidone) on silica. J. Colloid and Interface Sci., 97:526-535; Esumi, Kunio and Oyama, Michiyo (1993) Simultaneous sorption of poly(vinylpyrrolidone) and cationic surfactant from their mixed solutions on silica. Langmuir, 9:2020-2023; Gun=ko, V. M., Zarko, E. F., Voroin, E. F., Turov, V. V., Mironyuk, I. F., Gerashchenko, I. I., Goncharuk, E. V. Pakhlov, E. M., Guzenko, N. V., Leboda, R., Skubiszewska-Zieba, J., Janusz, W., Chibowski, S., Levchunk, Yu. N., and Klyueva, A. V. (2002) Impact of some organics on structural and sorptive characteristics of fumed silica in different media. Langmuir, 18:581-596; and Thibaut, A., Misselyn-Bauduin, A. M., Broze, G. and Jérôme, R. (2000) Sorption of poly(vinylpyrrolidone)/Surfactant(s) mixtures at the silica/water interface. Langmuir, 16:9841-9849), on alumina (see e.g., Otsuka, H. and Esumi, K. (1994) Simultaneous sorption of poly(vinylpyrrolidone) and anionic hydrocarbon/fluorocarbon surfactant from their binary mixtures on alumina. Langmuir, 10:45-50; Esmui, K., Takaku, Y. and Otsuka, H. (1994) Introduction between aerosol OT and poly(vinylpyrrolidone) on alumina. Langmuir, 10:3250-3254; and Esmui, K., Iitaka, M. and Torigoe, K. (2000) Kinetics of simultaneous sorption of poly(vinylpyrrolidone) and sodium dodecyl sulfate on alumina particles. J. Colloid and Interface Sci., 232:71-75), on kaolinite (see e.g., Israel, L., Güler, C., Yilmaz, H., and Güler, S. (2001) The sorption of polyvinylpyrrolidone on kaolinite with sodium chloride., J. Colloid and Interface Sci., 238:80-84), and on zirconium (see e.g., Rovira-Bru, M., Giralt, F. and Cohen, Y. (2001) Protein sorption onto zirconia modified with terminally grafted polyvinylpyrrolidone., J. Colloid and Interface Sci., 235:70-79). There have also been more general studies of the binding configuration and structure of PVP both on surfaces and in solution (see e.g., Barnett, K. G., Cosgrove, T., Vincent, B. and Sissons, D. S. (1981) Measurement of the polymerbound fraction at the solid-liquid interface by pulsed nuclear magnetic resonance. Macromolecules, 1981:1018-1020; Gargallo, L., Pérez-Cotapos, J., Santos, J. G. and Radic D. (1993) Poly(N-vinyl-2-pyrrolidone)-monoalkyl xanthates. 1. Sorption and chemical reaction. Langmuir; 681-684; Misselyn-Bauduin, A., Thibaut, A. Grandjean, J, Broze, G. and Jérôme, R. (2001) Investigation of the interactions of polyvinylpyrrolidone with mixtures of anionic and nonionic surfactants or anionic and zwitterionic surfactant by pulsed field gradient NMR., J. Colloid and Interface Sci., 238:1-7; Smith, J. N., Meadows, J. and Williams, P. A. (1996) Sorption of polyvinylpyrrolidone onto polystyrene lattices and the effect on colloid stability. Langmuir, 12:3773-3778; and Sun, T and King, H. E. (1996) Aggregation behavior in the semidilute poly(N-vinyl-2-pyrrolidone)/water system. Macromolecules, 29:3175-3181). Most of these studies were broadly aimed at understanding how PVP sorption can be used to modify colloid particle surfaces for better dispersion during industrial applications. Additionally, PVP 10K has been used to intercalate illite fundamental particles for XRD analysis (Eberl, D D; Drits, V A; Srodoñ, J; Nueesch, R (1996) MUDMASTER; a program for calculating crystallite size distributions and strain from the shapes of X-ray diffraction peaks. U.S. Geol. Sur. Report, OF 96-0171; Eberl et al., 1998, identified above; and Uhlik, P., {hacek over (S)}ucha, V., Elsass, F., and Caplovicova, M. (2000) High-resolution transmission electron microscopy of mixed-layer clays dispersed in PVP-10; A new technique to distinguish detrital and authigenic illitic material. Clay Min., 35:781-789), such that when the PVP/clay suspension is evaporated, the PVP widely separates the illite particles, eliminating interparticle diffraction, and allowing the quantification of illite particle thicknesses from the broadening of the (001) peak.
There is a need in the art for improvements in the measurement of the surface area of smectite crystals. The present invention addresses this and other needs.